1. Field of the Invention
The present invention relates to improvements in ultrasound visualization systems. More particularly, the present invention relates to improvements in the transceiver or "head" circuitry for selectively switching and driving transducers in a linear phased array format, and further relates to improvements in scan conversion from relatively slow ultrasound scan rate to a scan rate which is suitable for television display in a real time format.
2. Description of the Prior Art
In recent years ultrasound visualization systems have played an increasingly important role in medical diagnostics. Ultrasound systems present the significant advantages over x-ray systems because they do not involve radiation exposure, and they are capable of detecting subtle changes in soft tissues which are not otherwise distinguishable by x-ray systems. Ultrasound visualization systems also have a number of useful applications in fields other than medical diagnostics.
Ultrasound visualization systems obtain an ultrasound scan signal which is reresentative of an object being observed by directing accoustical pulses into the object and by processing the echo signals which are subsequently received. The scan rate of a received ultrasound signal, however, is much slower than the scan rate which would be required for a real time television display. Therefore, a scan conversion system is required to convert the scan rate of the ultrasound scan signal into a signal suitable for a display television. It is known in the prior art to provide the conversion by translating the ultrasound signal into digital data wherein each digital number represents the amplitude for a given point in the scan signal, to store the data in a buffer, and to reconvert the data into a television raster scan signal at a scan rate which is suitable for real time display.
In the communications art, delta modulation has been used in which an analog signal is periodically varied in response to relative changes in a signal to be transmitted. The delta signal is then transmitted and is subsequently decoded by an analog following circuit at the receiving end of the transmission. In this manner, audio and video signals can be transmitted using a relatively narrow band width. In order to be able to reproduce sharp changes in the amplitude signal, and thereby maintain good resolution, various complicated mathematical schemes have been devised. Also, a very high frequency sampling rate must be maintained in order to maintain quality in the received signal.